Integration of ALD tantalum nitride and alpha-phase tantalum for copper metallization application

ABSTRACT

A method for forming a metal interconnect on a substrate is provided. In one aspect, the method comprises depositing a refractory metal containing barrier layer having a thickness that exhibits a crystalline like structure and is sufficient to inhibit atomic migration on at least a portion of a metal layer by alternately introducing one or more pulses of a metal-containing compound and one or more pulses of a nitrogen-containing compound; depositing a seed layer on at least a portion of the barrier layer; and depositing a second metal layer on at least a portion of the seed layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. Provisional PatentApplication Serial No. 60/346,086, filed on Oct. 26, 2001, and entitled“Method and Apparatus for ALD Deposition”, which is incorporated byreference herein. This application also claims benefit of U.S. patentapplication, Ser. No. 09/965,370, filed on Sep. 26, 2001, and entitled“Integration of Barrier Layer and Seed Layer”, which is incorporated byreference herein. This application also claims benefit of U.S. patentapplication Ser. No. 09/965,373, filed on Sep. 26, 2001, and entitled“Integration of Barrier Layer and Seed Layer”, which is incorporated byreference herein. This application further claims benefit of U.S. patentapplication Ser. No. 09/965,369, filed on Sep. 26, 2001, and entitled“Integration of Barrier Layer and Seed Layer”, which is incorporated byreference herein. This application further claims benefit of U.S. patentapplication Ser. No. 10/193,333, filed on Jul. 10, 2002, and entitled“Integration of Barrier Layer and Seed Layer”, which is incorporated byreference herein. This application further claims benefit of U.S. patentapplication Ser No. 10/199,415, filed on Jul. 18, 2002, entitled“Enhanced Copper Growth With Ultrathin Barrier Layer For HighPerformance Interconnects”, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] Embodiments of the present invention relate to a method formanufacturing integrated circuit devices. More particularly, embodimentsof the invention relate to forming metal interconnect structures usingone or more cyclical deposition processes.

[0004] 2. Description of the Related Art

[0005] As the structure size of integrated circuit (IC) devices isscaled down to sub-quarter micron dimensions, electrical resistance andcurrent densities have become an area for concern and improvement.Multilevel interconnect technology provides the conductive pathsthroughout an IC device, formed in high aspect ratio features, includingcontacts, plugs, vias, lines, wires, and other features. A typicalprocess for forming an interconnect on a substrate includes depositingone or more layers, etching at least one of the layer(s) to form one ormore features, depositing a barrier layer in the feature(s) anddepositing one or more layers to fill the feature. Typically, a featureis formed within a dielectric material disposed between a lowerconductive layer and an upper conductive layer. The interconnect isformed within the feature to link the upper and lower conductive layers.Reliable formation of these interconnect features is important to theproduction of the circuits and to continued effort to increase circuitdensity and quality on individual substrates and die.

[0006] Copper has recently become a choice metal for filling sub-micronhigh aspect ratio interconnect features because copper and its alloyshave lower resistivities than aluminum. However, copper diffuses morereadily into surrounding materials and can alter the electronic devicecharacteristics of the adjacent layers and, for example, form aconductive path between layers, thereby reducing the reliability of theoverall circuit and possibly resulting in device failure.

[0007] Barrier layers therefore, are deposited prior to coppermetallization to prevent or impede the diffusion of copper atoms.Barrier layers typically contain a refractory metal such as tungsten,titanium, tantalum, and nitrides thereof, all of which have a greaterresistivity than copper. To deposit a barrier layer within a feature,the barrier layer must be deposited on the bottom of the feature as wellas the sidewalls thereof. Therefore, the additional amount of thebarrier layer on the bottom of the feature not only increases theoverall resistance of the feature, but also forms an obstruction betweenhigher and lower metal interconnects of a multi-layered interconnectstructure.

[0008] There is a need, therefore, for an improved method for formingmetal interconnect structures which minimizes the electrical resistanceof the interconnect.

SUMMARY OF THE INVENTION

[0009] A method for forming a metal interconnect on a substrate isprovided. In one aspect, the method comprises depositing a refractorymetal containing barrier layer having a thickness that exhibits acrystalline like structure and is sufficient to inhibit atomic migrationon at least a portion of a metal layer. The interconnect is produced byalternately introducing one or more pulses of a metal-containingcompound and one or more pulses of a nitrogen-containing compound,depositing a seed layer on at least a portion of the barrier layer, anddepositing a second metal layer on at least a portion of the seed layer.

[0010] In another aspect, the method comprises depositing a first metallayer on a substrate surface; depositing a titanium silicon nitridelayer having a thickness less than about 20 angstroms over at least aportion of the first metal layer by alternately introducing one or morepulses of a titanium-containing compound, one or more pulses of asilicon-containing compound, and one or more pulses of anitrogen-containing compound; depositing a dual alloy seed layer, anddepositing a second metal layer on at least a portion of the dual alloyseed layer.

[0011] In yet another aspect, the method comprises depositing a bilayerbarrier having a thickness less than about 20 angstroms on at least aportion of a metal layer, depositing a dual alloy seed layer, anddepositing a second metal layer on at least a portion of the dual alloyseed layer. The bilayer barrier comprises a first layer of tantalumnitride deposited by alternately introducing one or more pulses of atantalum-containing compound and one or more pulses of anitrogen-containing compound and a second layer of alpha phase tantalum;

[0012] In still yet another aspect, the method includes depositing afirst metal layer on a substrate surface; depositing a tantalum nitridebarrier layer having a thickness less than about 20 angstroms on atleast a portion of the first metal layer by alternately introducing oneor more pulses of a tantalum-containing compound and one or more pulsesof a nitrogen-containing compound depositing a dual alloy seed layercomprising copper and a metal selected from the group consisting ofaluminum, magnesium, titanium, zirconium, tin, and combinations thereofand depositing a second metal layer on at least a portion of the dualalloy seed layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features of thepresent invention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

[0014]FIG. 1 illustrates processing sequences according to variousembodiments of the invention described herein.

[0015] FIGS. 2A-2D are schematic cross section views of an exemplarywafer at different stages of an interconnect fabrication sequenceaccording to embodiments described herein.

[0016]FIG. 3 illustrates a schematic, partial cross section of anexemplary processing chamber 200 for forming a thin barrier layeraccording to a cyclical deposition technique described herein.

[0017]FIG. 4 illustrates a schematic plan view of an exemplaryintegrated cluster tool adaptable to perform the interconnectfabrication sequence described herein.

[0018]FIG. 5 is a transmission electron microscope (TEM) image of afeature having a titanium nitride barrier layer deposited thereinaccording to the deposition techniques described herein.

[0019]FIG. 6 is a TEM image showing a partial cross sectional view of amultilevel, interconnect structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] A process sequence for forming one or more interconnectstructures is provided. Interconnect structures formed according toembodiments described herein have an overall lower resistivity andbetter electrical properties than interconnects of the prior art, andare particularly useful for making memory and logic structures for usewith the fabrication of integrated circuits. The formation of theinterconnect structures includes the formation of a thin barrier layerat least partially deposited on an underlying metal layer, a seed layerat least partially deposited on the barrier layer, and a bulk metallayer at least partially deposited on the seed layer. The term“interconnect” as used herein refers to any conductive path formedwithin an integrated circuit. The term “bulk metal” as used hereinrefers to a greater amount of metal deposited in relation to othermetals deposited to form the interconnect structure.

[0021]FIG. 1 illustrates the process sequence according to embodimentsof the invention. A thin barrier layer is first deposited at leastpartially on an underlying substrate surface, such as a lower levelmetal interconnect or a metal gate, for example, as shown at step 480.The barrier layer is deposited according to a cyclical layer depositiontechnique described herein to provide excellent barrier properties andpermit the continuous growth of the underlying metal layer across thebarrier layer, into an upper level metal interconnect or subsequentlydeposited metal layer. In one aspect, the barrier layer is a refractorymetal-containing layer, such as tantalum, titanium, and tungsten, forexample, and may include a refractory metal nitride material, such astantalum nitride (TaN). In another aspect, the barrier layer is a thinbi-layer of TaN and alpha-phase tantalum. In yet another aspect, thebarrier layer may be a ternary material formed from a refractory metalcontaining compound, a silicon-containing compound and anitrogen-containing compound. The barrier layer may also act as awetting layer, adhesion layer, or glue layer for subsequentmetallization.

[0022] A “thin layer” as used herein refers to a layer of materialdeposited on a substrate surface having a thickness of about 20angstroms (Å) or less, such as about 10 Å. The thickness of the barrierlayer is so thin that electrons of the adjacent metal interconnects cantunnel through the barrier layer. Accordingly, the barrier layersignificantly enhances the metal interconnect electrical performance bylowering the overall electrical resistance and providing good devicereliability.

[0023] The thin barrier layer deposited according to the cyclicaldeposition methods described herein shows evidence of an epitaxialgrowth phenomenon. In other words, the barrier layer takes on the sameor substantially the same crystallographic characteristics as theunderlying layer. As a result, a substantially single crystal is grownsuch that there is no void formation at an interface between the barrierlayer and the underlying layer. Likewise, subsequent metal layersdeposited over the barrier layer exhibit the same or substantially thesame epitaxial growth characteristics that continue the formation of thesingle crystal. Accordingly, no void formation is produced at thisinterface. The resulting structure resembling a single crystaleliminates voids formation, thereby substantially increasing devicereliability. The single crystal structure also reduces the overallresistance of the interconnect feature while still providing excellentbarrier properties. Furthermore, it is believed that the singlecrystalline growth reduces the susceptibility of electromigration andstress migration due to the conformal and uniform crystallineorientation across the interconnect material interfaces.

[0024] “Cyclical deposition” as used herein refers to the sequentialintroduction of two or more reactive compounds to deposit a mono layerof material on a substrate surface. The two or more reactive compoundsare alternatively introduced into a reaction zone of a processingchamber. Each reactive compound is separated by a time delay to alloweach compound to adhere and/or react on the substrate surface. In oneaspect, a first precursor or compound A is pulsed into the reaction zonefollowed by a first time delay. Next, a second precursor or compound Bis pulsed into the reaction zone followed by a second delay. When aternary material is desired, such as titanium silicon nitride, forexample, a third compound (C), is dosed/pulsed into the reaction zonefollowed by a third time delay. During each time delay an inert gas,such as argon, is introduced into the processing chamber to purge thereaction zone or otherwise remove any residual reactive compound fromthe reaction zone. Alternatively, the purge gas may flow continuouslythroughout the deposition process so that only the purge gas flowsduring the time delay between pulses of reactive compounds. The reactivecompounds are alternatively pulsed until a desired film or filmthickness is formed on the substrate surface.

[0025] A “substrate surface”, as used herein, refers to any substratesurface upon which film processing is performed. For example, asubstrate surface may include silicon, silicon oxide, doped silicon,germanium, gallium arsenide, glass, sapphire, and any other materialssuch as metals, metal nitrides, metal alloys, and other conductivematerials, depending on the application. A substrate surface may alsoinclude dielectric materials such as silicon dioxide and carbon dopedsilicon oxides.

[0026] A “pulse” or “dose” as used herein is intended to refer to aquantity of a particular compound that is intermittently ornon-continuously introduced into a reaction zone of a processingchamber. The quantity of a particular compound within each pulse mayvary over time, depending on the duration of the pulse. The duration ofeach pulse is variable depending upon a number of factors such as, forexample, the volume capacity of the process chamber employed, the vacuumsystem coupled thereto, and the volatility/reactivity of the particularcompound itself.

[0027] The term “compound” is intended to include one or moreprecursors, oxidants, reductants, reactants, and catalysts, or acombination thereof. The term “compound” is also intended to include agrouping of compounds, such as when two or more compounds are introducedin a processing system at the same time. For example, a grouping ofcompounds may include one or more catalysts and one or more precursors.The term “compound” is further intended to include one or moreprecursors, oxidants, reductants, reactants, and catalysts, or acombination thereof in an activated or otherwise energized state, suchas by disassociation or ionization.

[0028] It is believed that the surface attraction used to physisorb,adsorb, absorb, or chemisorb a monolayer of reactants on a substratesurface are self-limiting in that only one monolayer may be depositedonto the substrate surface during a given pulse because the substratesurface has a finite number of sites available for the reactants. Oncethe finite number of sites is occupied by the reactants, furtherdeposition of the reactants will be blocked. The cycle may be repeatedto a desired thickness of the layer.

[0029] Still referring to FIG. 1, a seed layer is at least partiallydeposited on the barrier layer, as shown at step 485. The seed layer maybe deposited using any conventional deposition technique, such aschemical vapor deposition (CVD), physical vapor deposition (PVD),electroplating, or electroless plating. Preferably, the seed layer isdeposited conformally on the underlying barrier layer to have athickness between about 100 Å and about 500 Å. In one aspect, the seedlayer is a conventional copper seed layer. In another aspect, the seedlayer is a dual alloy seed layer. Exemplary dual alloy seed layersinclude: 1) undoped copper deposited utilizing a target containingundoped copper, 2) a copper alloy containing aluminum in a concentrationof about 2.0 atomic percent deposited utilizing a copper-aluminum targetcomprising aluminum in a concentration of about 2.0 atomic percent, 3) acopper alloy containing tin in a concentration of about 2.0 atomicpercent deposited utilizing a copper-tin target comprising tin in aconcentration of about 2.0 atomic percent, and 4) a copper alloycontaining zirconium in a concentration of about 2.0 atomic percentdeposited utilizing a copper-zirconium target comprising zirconium in aconcentration of about 2.0 atomic percent.

[0030] The bulk metal layer is at least partially deposited on the seedlayer, as shown at step 487. The metal layer may also be deposited usingany conventional deposition technique, such as chemical vapor deposition(CVD), physical vapor deposition (PVD), electroplating, or electrolessplating. The metal layer preferably includes any conductive materialsuch as aluminum, copper, tungsten, or combinations thereof, forexample.

[0031] FIGS. 2A-2D are schematic representations of an exemplaryinterconnect structure at different stages of fabrication. FIG. 2A showsan underlying metal layer 110 having a dielectric layer 112 formedthereon. FIG. 2B shows a barrier layer 130 at least partially depositedon the underlying metal layer 110. The underlying metal layer 110 maycontain any conductive metal such as aluminum, copper, tungsten, orcombinations thereof, for example, and may form part of an interconnectfeature such as a plug, via, contact, line, wire, and may also be partof a metal gate electrode. FIG. 2C shows a seed layer 140 at leastpartially deposited on the barrier layer 130, and FIG. 2D shows a bulkmetal layer 142 at least partially deposited on the seed layer 140.

[0032] Referring to FIG. 2A, the dielectric layer 112 may be anydielectric material including a low k dielectric material (k≦4.0),whether presently known or yet to be discovered. For example, thedielectric layer 112 may be a silicon oxide or a carbon doped siliconoxide, for example. The dielectric layer 112 has been etched to form afeature 114 therein using conventional and well-known techniques. Thefeature 114 may be a plug, via, contact, line, wire, or any otherinterconnect component. Typically, the feature 114 has verticalsidewalls 116 and a floor 118, having an aspect ratio of about 4:1 orgreater, such as about 6:1. The floor 118 exposes at least a portion ofthe lower level metal interconnect 110.

[0033] Referring to FIG. 2B, the barrier layer 130 is conformallydeposited on the floor 118 as well as the side walls 116 of the feature114. Preferably, the barrier layer contains tantalum nitride depositedto a thickness of about 20 Å or less, preferably about 10 Å, byproviding one or more pulses of a tantalum-containing compound at a flowrate between about 100 sccm and about 1,000 sccm for a time period ofabout 1.0 second or less and one or more pulses of a nitrogen-containingcompound at a flow rate between about 100 sccm and about 1,000 sccm fora time period of about 1.0 second or less to a reaction zone having asubstrate disposed therein. Exemplary tantalum-containing compoundsinclude: t-butylimino tris(diethylamino) tantalum (TBTDET); pentakis(ethylmethylamino); tantalum (PEMAT); pentakis (dimethylamino) tantalum(PDMAT); pentakis (diethylamino) tantalum (PDEAT); t-butyliminotris(diethyl methylamino) tantalum(TBTMET); t-butylimino tris(dimethylamino) tantalum (TBTDMT); bis(cyclopentadienyl) tantalum trihydride((Cp)₂TaH₃); bis(methylcyclopentadienyl) tantalum trihydride((CpMe)₂TaH₃); derivatives thereof; and combinations thereof. Exemplarynitrogen-containing compounds include: ammonia; hydrazine;methylhydrazine; dimethylhydrazine; t-butylhydrazine; phenylhydrazine;azoisobutane; ethylazide; derivatives thereof; and combinations thereof.

[0034] It is to be understood that these compounds or any other compoundnot listed above may be a solid, liquid, or gas at room temperature. Forexample, PDMAT is a solid at room temperature and TBTDET is a liquid atroom temperature. Accordingly, the non-gas phase precursors aresubjected to a sublimation or vaporization step, which are both wellknown in the art, prior to introduction into the processing chamber. Acarrier gas, such as argon, helium, nitrogen, hydrogen, or a mixturethereof, may also be used to help deliver the compound into theprocessing chamber, as is commonly known in the art.

[0035] Each pulse is performed sequentially, and is accompanied by aseparate flow of non-reactive gas at a rate between about 200 sccm andabout 1,000 sccm. The separate flow of non-reactive gas may be pulsedbetween each pulse of the reactive compounds or the separate flow ofnon-reactive gas may be introduced continuously throughout thedeposition process. The separate flow of non-reactive gas, whetherpulsed or continuous, serves to remove any excess reactants from thereaction zone to prevent unwanted gas phase reactions of the reactivecompounds, and also serves to remove any reaction by-products from theprocessing chamber, similar to a purge gas. In addition to theseservices, the continuous separate flow of non-reactive gas helps deliverthe pulses of reactive compounds to the substrate surface similar to acarrier gas. The term “non-reactive gas” as used herein refers to asingle gas or a mixture of gases that does not participate in the metallayer formation. Exemplary non-reactive gases include argon, helium,nitrogen, hydrogen, and combinations thereof.

[0036] A “reaction zone” is intended to include any volume that is influid communication with a substrate surface being processed. Thereaction zone may include any volume within a processing chamber that isbetween a gas source and the substrate surface. For example, thereaction zone includes any volume downstream of a dosing valve in whicha substrate is disposed.

[0037] The durations for each pulse/dose are variable and may beadjusted to accommodate, for example, the volume capacity of theprocessing chamber as well as the capabilities of a vacuum systemcoupled thereto. Additionally, the dose time of a compound may varyaccording to the flow rate of the compound, the pressure of thecompound, the temperature of the compound, the type of dosing valve, thetype of control system employed, as well as the ability of the compoundto adsorb onto the substrate surface. Dose times may also vary basedupon the type of layer being formed and the geometry of the device beingformed.

[0038] Typically, the duration for each pulse or “dose time” istypically about 1.0 second or less. However, a dose time can range frommicroseconds to milliseconds to seconds, and even to minutes. Ingeneral, a dose time should be long enough to provide a volume ofcompound sufficient to adsorb/chemisorb onto the entire surface of thesubstrate and form a layer of the compound thereon.

[0039]FIG. 3 illustrates a schematic, partial cross section of anexemplary processing chamber 200 capable of forming a barrier layerusing cyclical layer deposition, atomic layer deposition, digitalchemical vapor deposition, and rapid chemical vapor depositiontechniques. The terms “cyclical layer deposition”, “atomic layerdeposition”, “digital chemical vapor deposition”, and “rapid chemicalvapor deposition” are used interchangeably herein and refer to gas phasedeposition techniques whereby two or more compounds are sequentiallyintroduced into a reaction zone of a processing chamber to deposit athin layer of material on a substrate surface. Such a processing chamber200 is available from Applied Materials, Inc. located in Santa Clara,Calif., and a brief description thereof follows. A more detaileddescription may be found in commonly assigned U.S. patent applicationSer. No. 10/032,284, entitled “Gas Delivery Apparatus and Method ForAtomic Layer Deposition”, filed on Dec. 21, 2001, which is incorporatedherein by reference.

[0040] The processing chamber 200 may be integrated into an integratedprocessing platform, such as an Enduram™ platform also available fromApplied Materials, Inc. Details of the Endura™ platform are described incommonly assigned U.S. patent application Ser. No. 09/451,628, entitled“Integrated Modular Processing Platform”, filed on Nov. 30, 1999, whichis incorporated by reference herein.

[0041] Referring to FIG. 3, the chamber 200 includes a chamber body 202having a slit valve 208 formed in a sidewall 204 thereof and a substratesupport 212 disposed therein. The substrate support 212 is mounted to alift motor 214 to raise and lower the substrate support 212 and asubstrate 210 disposed thereon. The substrate support 212 may alsoinclude a vacuum chuck, an electrostatic chuck, or a clamp ringfor-securing the substrate 212 to the substrate support 212 duringprocessing. Further, the substrate support 212 may be heated using anembedded heating element, such as a resistive heater, or may be heatedusing radiant heat, such as heating lamps disposed above the substratesupport 212. A purge ring 222 may be disposed on the substrate support212 to define a purge channel 224 that provides a purge gas to preventdeposition on a peripheral portion of the substrate 210.

[0042] A gas delivery apparatus 230 is disposed at an upper portion ofthe chamber body 202 to provide a gas, such as a process gas and/or apurge gas, to the chamber 200. A vacuum system 278 is in communicationwith a pumping channel 279 to evacuate gases from the chamber 200 and tohelp maintain a desired pressure or a desired pressure range inside apumping zone 266 of the chamber 200.

[0043] The gas delivery apparatus 230 includes a chamber lid 232 havingan expanding channel 234 formed within a central portion thereof. Thechamber lid 232 also includes a bottom surface 260 extending from theexpanding channel 234 to a peripheral portion of the chamber lid 232.The bottom surface 260 is sized and shaped to substantially cover thesubstrate 210 disposed on the substrate support 212. The expandingchannel 234 has an inner diameter that gradually increases from an upperportion 237 to a lower portion 235 adjacent the bottom surface 260 ofthe chamber lid 232. The velocity of a gas flowing therethroughdecreases as the gas flows through the expanding channel 234 due to theexpansion of the gas. The decreased gas velocity reduces the likelihoodof blowing off reactants adsorbed on the surface of the substrate 210.

[0044] The gas delivery apparatus 230 also includes at least two highspeed actuating valves 242 having one or more ports. At least one valve242 is dedicated to each reactive compound. For example, a first valveis dedicated to a refractory metal-containing compound, such as tantalumand titanium, and a second valve is dedicated to a nitrogen-containingcompound. When a ternary material is desired, a third valve is dedicatedto an additional compound. For example, if a silicide is desired, theadditional compound may be a silicon-containing compound.

[0045] The valves 242 may be any valve capable of precisely andrepeatedly delivering short pulses of compounds into the chamber body202. In some cases, the on/off cycles or pulses of the valves 242 may beas fast as about 100 msec or less. The valves 242 can be directlycontrolled by a system computer, such as a mainframe for example, orcontrolled by a chamber/application specific controller, such as aprogrammable logic computer (PLC) which is described in more detail inthe co-pending U.S. patent application Ser. No. 09/800,881, entitled“Valve Control System For ALD Chamber”, filed on Mar. 7, 2001, which isincorporated by reference herein. For example, the valves 242 may beelectronically controlled (EC) valves, which are commercially availablefrom Fujikin of Japan as part number FR-21-6.35 UGF-APD.

[0046] To facilitate the control and automation of the overall system,the integrated processing system may include a controller 140 comprisinga central processing unit (CPU) 142, memory 144, and support circuits146. The CPU 142 may be one of any form of computer processors that areused in industrial settings for controlling various drives andpressures. The memory 144 is connected to the CPU 142, and may be one ormore of a readily available memory such as random access memory (RAM),read only memory (ROM), floppy disk, hard disk, or any other form ofdigital storage, local or remote. Software instructions and data can becoded and stored within the memory 144 for instructing the CPU 142. Thesupport circuits 146 are also connected to the CPU 142 for supportingthe processor 142 in a conventional manner. The support circuits 146 mayinclude cache, power supplies, clock circuits, input/output circuitry,subsystems, and the like.

[0047] In a particular embodiment, a TaN barrier layer is formed bycyclically introducing PDMAT and ammonia to the substrate surface. Toinitiate the cyclical deposition of the TaN layer, a carrier/inert gassuch as argon is introduced into the processing chamber 200 to stabilizethe pressure and temperature therein. The carrier gas is allowed to flowcontinuously during the deposition process such that only the argonflows between pulses of each compound. A first pulse of PDMAT isprovided from the gas source 238 at a flow rate between about betweenabout 100 sccm and about 400 sccm, with a pulse time of about 0.6seconds or less after the chamber temperature and pressure have beenstabilized at about 200° C. to about 300° C. and about 1 Torr to about 5Torr. A pulse of ammonia is then provided from the gas source 239 at aflow rate between about 200 sccm and about 600 sccm, with a pulse timeof about 0.6 seconds or less.

[0048] A pause between pulses of PDMAT and ammonia is about 1.0 secondor less, preferably about 0.5 seconds or less, more preferably about 0.1seconds or less. In various aspects, a reduction in time between pulsesat least provides higher throughput. As a result, a pause after thepulse of ammonia is also about 1.0 second or less, about 0.5 seconds orless, or about 0.1 seconds or less. Argon gas flowing between about 100sccm and about 1000 sccm, such as between about 100 sccm and about 400sccm, is continuously provided from the gas source 240 through eachvalve 242. In one aspect, a pulse of PDMAT may still be in the chamberwhen a pulse of ammonia enters. In general, the duration of the carriergas and/or pump evacuation should be long enough to prevent the pulsesof PDMAT and ammonia from mixing together in the reaction zone.

[0049] The heater temperature is maintained between about 100° C. andabout 300° C. at a chamber pressure between about 1.0 and about 5.0Torr. Preferably, the deposition temperature is between about 200° C.and about 250° C. Each cycle consisting of a pulse of PDMAT, pause,pulse of ammonia, and pause provides a tantalum nitride layer having athickness between about 0.3 Å and about 1.0 Å per cycle. The alternatingsequence may be repeated until the desired thickness is achieved, whichis less than about 20 Å, such as about 10 Å. Accordingly, the depositionmethod requires between 10 and 70 cycles, more typically between 20 and30 cycles.

[0050] In another aspect, a ternary barrier layer having a thicknessless than about 20 Å, such as 10 Å, is deposited by providing one ormore pulses of a refractory metal-containing compound, one or morepulses of a nitrogen-containing compound, and one or more pulses of asilicon-containing compound. Each pulse is adjusted to provide adesirable composition, silicon incorporation level, thickness, density,and step coverage of the refractory metal silicon nitride layer. A“ternary barrier layer” as used herein refers to a material having acomposition comprising three major elements, such as titanium, nitrogenand silicon. An exemplary “ternary barrier layer” may also includetantalum, nitrogen and silicon.

[0051] Each pulse is performed sequentially, and is accompanied by aseparate flow of carrier/inert gas at the same process conditionsdescribed above. The separate flow of carrier/inert gas may be pulsedbetween each pulse of reactive compound or the separate flow ofcarrier/inert gas may be introduced continuously throughout thedeposition process.

[0052] Preferably, the ternary barrier layer contains titanium siliconnitride. In this embodiment, each cycle consists of a pulse of atitanium-containing compound, a pause, a pulse of a silicon-containingcompound, a pause, a pulse of a nitrogen-containing compound, and apause. Exemplary titanium-containing compound include tetrakis(dimethylamino) titanium (TDMAT), tetrakis (ethylmethylamino) titanium(TEMAT), tetrakis (diethylamino) titanium (TDEAT), titaniumtetrachloride (TiCl₄), titanium iodide (TiI₄), titanium bromide (TiBr₄),and other titanium halides. Exemplary silicon-containing compoundsinclude silane, disilane, methylsilane, dimethylsilane, chlorosilane(SiH₃Cl), dichlorosilane (SiH₂Cl₂), and trichlorosilane (SiHCl₃).Exemplary nitrogen-containing compounds include: ammonia; hydrazine;methylhydrazine; dimethylhydrazine; t-butylhydrazine; phenylhydrazine;azoisobutane; ethylazide; derivatives thereof; and combinations thereof.

[0053] To initiate the cyclical deposition of a Ti_(x)Si_(y)N layer,argon is introduced into the processing chamber 200 to stabilize thepressure and temperature therein. This separate flow of argon flowscontinuously during the deposition process such that only the argonflows between pulses of each compound. The separate flow of argon flowsbetween about 100 sccm and about 1000 sccm, such as between about 100sccm and about 400 sccm. In one aspect, a pulse of TDMAT is provided ata flow rate between about between about 10 sccm and about 1000 sccm,with a pulse time of about 0.6 seconds or less after the chamberpressure and temperature have been stabilized at about 250° C. and 2Torr. A pulse of silane is then provided at a flow rate between about 5sccm and about 500 sccm, with a pulse time of 1 second or less. A pulseof ammonia is then provided at a flow rate between about 100 sccm andabout 5,000 sccm, with a pulse time of about 0.6 seconds or less.

[0054] A pause between pulses of TDMAT and silane is about 1.0 second orless, preferably about 0.5 seconds or less, more preferably about 0.1seconds or less. A pause between pulses of silane and ammonia is about1.0 second or less, about 0.5 seconds or less, or about 0.1 seconds orless. A pause after the pulse of ammonia is also about 1.0 second orless, about 0.5 seconds or less, or about 0.1 seconds or less. In oneaspect, a pulse of TDMAT may still be in the chamber when a pulse ofsilane enters, and a pulse of silane may still be in the chamber when apulse of ammonia enters.

[0055] The heater temperature is maintained between about 100° C. andabout 300° C. at a chamber pressure between about 1.0 and about 5.0Torr. Each cycle consisting of a pulse of TDMAT, pause, pulse of silane,pause, pulse of ammonia, and pause provides a titanium silicon nitridelayer having a thickness between about 0.3 Å and about 1.0 Å per cycle.The alternating sequence may be repeated until the desired thickness isachieved, which is less than about 20 Å, such as about 10 Å.Accordingly, the deposition method requires between 10 and 70 cycles.

[0056] In yet another aspect, an alpha phase tantalum (α-Ta) layerhaving a thickness of about 20 Å or less, such as about 10 Å, may bedeposited over at least a portion of the previously deposited binary(TaN) or ternary (TiSiN) layers. The α-Ta layer may be deposited usingconventional techniques, such as PVD and CVD for example, to form abilayer stack. For example, the bilayer stack may include a TaN portiondeposited by cyclical layer deposition described above and an α-Taportion deposited by high density plasma physical vapor deposition(HDP-PVD). An alpha phase tantalum is preferred due to its lowerresistance compared to a beta phase tantalum.

[0057] To further illustrate, the α-Ta portion of the stack may bedeposited using an ionized metal plasma (IMP) chamber, such as a Vectra™chamber, available from Applied Materials, Inc. of Santa Clara, Calif.The IMP chamber includes a target, coil, and biased substrate supportmember, and may also be integrated into an Endura™ platform, alsoavailable from Applied Materials, Inc. A power between about 0.5 kW andabout 5 kW is applied to the target, and a power between about 0.5 kWand 3 kW is applied to the coil. A power between about 200 W and about500 W at a frequency of about 13.56 MHz is also applied to the substratesupport member to bias the substrate. Argon is flowed into the chamberat a rate of about 35 sccm to about 85 sccm, and nitrogen may be addedto the chamber at a rate of about 5 sccm to about 100 sccm. The pressureof the chamber is typically between about 5 mTorr to about 100 mTorr,while the temperature of the chamber is between about 20° C. and about300° C.

[0058] The barrier layer films described above may benefit from a postdeposition treatment process, such as a plasma treatment process or achemical treatment process, for example. A plasma treatment process candecrease resistance and improve yield. A typical plasma treatment mayinclude an argon plasma, a nitrogen plasma, or a nitrogen and hydrogenplasma. The plasma treatment may be performed in the same depositionchamber in which the barrier layer deposition occurs or in a differentchamber. If the plasma treatment occurs in the same chamber, the plasmacan be an in situ plasma or a plasma delivered from a remote plasmasource, such as a remote inductively coupled source or a microwavesource.

[0059] While not wishing to be bound by theory, it is believed that aplasma treatment of a tantalum nitride film, for example, reduces thenitrogen content of one or more sublayers by sputtering off nitrogen,which in turn reduces resistivity. For example, a plasma treatment isbelieved to make a tantalum-nitride layer more tantalum-rich as comparedto a non-plasma treated tantalum-nitride layer. In other words, a 1:1Ta:N film may be converted to a 2:1 Ta:N film using a plasma treatmentprocess. Tantalum nitride films having a sheet resistance ofapproximately equal to or less than 1200 micro-ohms-cm for 0.004 micron(40 Angstrom) films may be achieved.

[0060] Additionally, other non-chemically reactive gases may be used forphysically displacing nitrogen from the barrier layer, such as neon(Ne), xenon (Xe), helium (He), and hydrogen (H₂), for example.Generally, it is more desirable to have a plasma-gas atom or moleculewith an atomic-mass closer to N than to Ta in order to have preferentialsputtering of the N. However, a chemically reactive process may be usedwhere a particular gas preferentially reacts for removal of N whileleaving Ta.

[0061] A chemical treatment process can also decrease resistance andimprove yield. A typical chemical treatment may include exposure toaluminum compounds or silicon compounds. These compounds can include,but are not limited to, DMAH, TMA, silane, dimethylsilane,trimethylsilane and other organosilane compounds. A chemical treatmentis typically operated at a pressure between about/Torr and about 10 Torrat a temperature between about 200° C. and about 400° C. Following achemical treatment, it has been observed that a tantalum nitride filmdeposited according to the methods described above shows an improvementin dewetting compared with no chemical treatment.

[0062] The post deposition treatment processes may be performed afterthe formation of the barrier layer. Alternatively, the treatments may beperformed between deposition of each monolayer or between deposition ofeach cycle. For example, a treatment process may take place afterapproximately every 0.003 to 0.005 microns (30 to 50 Angstroms) of layeror after approximately every 7 to 10 cycles.

[0063] Furthermore, the patterned or etched substrate dielectric layer112 may be cleaned to remove native oxides or other contaminants fromthe surface thereof prior to depositing the barrier layer 130. Forexample, reactive gases are excited into a plasma within a remote plasmasource chamber such as a Reactive Pre-clean chamber available fromApplied Materials, Inc., located in Santa Clara, Calif. Pre-cleaning mayalso be done within a metal CVD or PVD chamber by connecting the remoteplasma source thereto. Alternatively, metal deposition chambers havinggas delivery systems could be modified to deliver the pre-cleaning gasplasma through existing gas inlets such as a gas distribution showerheadpositioned above the substrate.

[0064] In one aspect, the reactive pre-clean process forms radicals froma plasma of one or more reactive gases such as argon, helium, hydrogen,nitrogen, fluorine-containing compounds, and combinations thereof. Forexample, a reactive gas may include a mixture of tetrafluorocarbon (CF₄)and oxygen (O₂), or a mixture of helium (He) and nitrogen trifluoride(NF₃). More preferably, the reactive gas is a mixture of helium andnitrogen trifluoride.

[0065] Following the argon plasma, the chamber pressure is increased toabout 140 mTorr, and a processing gas consisting essentially of hydrogenand helium is introduced into the processing region. Preferably, theprocessing gas comprises about 5% hydrogen and about 95% helium. Thehydrogen plasma is generated by applying between about 50 watts andabout 500 watts power. The hydrogen plasma is maintained for about 10seconds to about 300 seconds.

[0066] Referring again to FIG. 2C, the seed layer 140 may be depositedusing high density plasma physical vapor deposition (HDP-PVD) to enablegood conformal coverage. One example of a HDP-PVD chamber is theSelf-Ionized Plasma SIP™ chamber, available from Applied Materials, Inc.of Santa Clara, Calif., which may be integrated into an Endura™platform, available from Applied Materials, Inc. Of course, othertechniques, such as physical vapor deposition, chemical vapordeposition, electroless plating, and electroplating, may be used.

[0067] A typical SIP™ chamber includes a target, coil, and biasedsubstrate support member. To form the copper seed layer, a power betweenabout 0.5 kW and about 5 kW is applied to the target, and a powerbetween about 0.5 kW and 3 kW is applied to the coil. A power betweenabout 200 and about 500 W at a frequency of about 13.56 MHz is appliedto bias the substrate. Argon is flowed into the chamber at a rate ofabout 35 sccm to about 85 sccm, and nitrogen may be added to the chamberat a rate of about 5 sccm to about 100 sccm. The pressure of the chamberis typically between about 5 mTorr to about 100 mTorr.

[0068] Alternatively, a seed layer 140 containing a copper alloy may bedeposited by any suitable technique such as physical vapor deposition,chemical vapor deposition, electroless deposition, or a combination oftechniques. Preferably, the copper alloy seed layer 140 containsaluminum and is deposited using a PVD technique described above. Duringdeposition, the process chamber is maintained at a pressure betweenabout 0.1 mtorr and about 10 mtorr. The target includes copper andbetween about 2 and about 10 atomic weight percent of aluminum. Thetarget may be DC-biased at a power between about 5 kW and about 100 kW.The pedestal may be RF-biased at a power between about 10 W and about1000 W. The copper alloy seed layer 140 is deposited to a thickness ofat least about 5 Å, and between about 5 Å and about 500 Å.

[0069] Referring to FIG. 2D, the metal layer 142 may be formed, usingchemical vapor deposition (CVD), physical vapor deposition (PVD),electroplating, or a combination thereof. For example, an aluminum (Al)layer may be deposited from a reaction of a gas mixture containingdimethyl aluminum hydride (DMAH) and hydrogen (H₂) or argon (Ar) orother DMAH containing mixtures, a CVD copper layer may be deposited froma gas mixture containing Cu⁺²(hfac)₂ (copper hexafluoroacetylacetonate), Cu⁺²(fod)₂ (copper heptafluoro dimethyl octanediene),Cu⁺¹hfac TMVS (copper hexafluoro acetylacetonate trimethylvinylsilane),or combinations thereof, and a CVD tungsten layer may be deposited froma gas mixture containing tungsten hexafluoride (WF₆) and a reducing gas.A PVD layer can be deposited from a copper target, an aluminum target,or a tungsten target.

[0070] Moreover, the metal layer 142 may be a refractory metal compoundincluding but not limited to titanium (Ti), tungsten (W), tantalum (Ta),zirconium (Zr), hafnium (Hf), molybdenum (Mo), niobium (Nb), vanadium(V), and chromium (Cr), among others. Conventionally, a refractory metalis combined with reactive species, such as for example chlorine (Cl) orfluorine (F), and is provided with another gas to form a refractorymetal compound. For example, titanium tetrachloride (TiCl₄), tungstenhexafluoride (WF₆), tantalum pentachloride (TaCl₅), zirconiumtetrachloride (ZrCl₄), hafnium tetrachloride (HfCl₄), molybdenumpentachloride (MoCl₅), niobium pentachloride (NbCl₅), vanadiumpentachloride (VCl₅), or chromium tetrachloride (CrCl₄) may be used as arefractory metal-containing compound gas.

[0071] Preferably, the metal layer 142 is copper and is formed within anelectroplating cell, such as the Electra™ Cu ECP system, available fromApplied Materials, Inc., of Santa Clara, Calif. The Electra™ Cu ECPsystem may also be integrated into an Endura™ platform also availablefrom Applied Materials, Inc.

[0072] A copper electrolyte solution and copper electroplating techniqueis described in commonly assigned U.S. Pat. No. 6,113,771, entitled“Electro-deposition Chemistry”, which is incorporated by referenceherein. Typically, the electroplating bath has a copper concentrationgreater than about 0.7 M, a copper sulfate concentration of about 0.85,and a pH of about 1.75. The electroplating bath may also contain variousadditives as is well known in the art. The temperature of the bath isbetween about 15° C. and about 25° C. The bias is between about −15volts to about 15 volts. In one aspect, the positive bias ranges fromabout 0.1 volts to about 10 volts and the negatives bias ranges fromabout −0.1 to about −10 volts.

[0073] Optionally, a thermal anneal process may be performed followingthe metal layer 142 deposition whereby the wafer is subjected to atemperature between about 100° C. and about 400° C. for about 10 minutesto about 1 hour, preferably about 30 minutes. A carrier/purge gas suchas helium, hydrogen, nitrogen, or a mixture thereof is introduced at arate of about 100 sccm to about 10,000 sccm. The chamber pressure ismaintained between about 2 Torr and about 10 Torr. The RF power is about200 W to about 1,000 W at a frequency of about 13.56 MHz, and thepreferable substrate spacing is between about 300 mils and about 800mils.

[0074] Following deposition, the top portion of the resulting structuremay be planarized. A chemical mechanical polishing (CMP) apparatus maybe used, such as the Mirra™ System available from Applied Materials,Santa Clara, Calif., for example. Optionally, the intermediate surfacesof the structure may be planarized between the deposition of thesubsequent layers described above.

[0075]FIG. 4 is a schematic top-view diagram of an exemplarymulti-chamber processing system 600 that may be adapted to perform thedeposition sequence disclosed above. Such a processing system 600 may bean Endura™ system, commercially available from Applied Materials, Inc.,of Santa Clara, Calif. A similar multi-chamber processing system isdisclosed in U.S. Pat. No. 5,186,718, entitled “Stage Vacuum WaferProcessing System and Method,” issued on Feb. 16,1993, which isincorporated by reference herein.

[0076] The system 600 generally includes load lock chambers 602, 604 forthe transfer of substrates into and out from the system 600. Typically,since the system 600 is under vacuum, the load lock chambers 602, 604may “pump down” the substrates introduced into the system 600. A firstrobot 610 may transfer the substrates between the load lock chambers602, 604, and a first set of one or more substrate processing chambers612, 614, 616, 618 (four are shown). Each processing chamber 612, 614,616, 618, can be outfitted to perform a number of substrate processingoperations such as cyclical layer deposition, chemical vapor deposition(CVD), physical vapor deposition (PVD), etch, pre-clean, degas,orientation and other substrate processes. The first robot 610 alsotransfers substrates to/from one or more transfer chambers 622, 624.

[0077] The transfer chambers 622, 624, are used to maintain ultrahighvacuum conditions while allowing substrates to be transferred within thesystem 600. A second robot 630 may transfer the substrates between thetransfer chambers 622, 624 and a second set of one or more processingchambers 632, 634, 636, 638. Similar to processing chambers 612, 614,616, 618, the processing chambers 632, 634, 636, 638 can be outfitted toperform a variety of substrate processing operations, such as cyclicallayer deposition, chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, and orientation, for example.Any of the substrate processing chambers 612, 614, 616, 618, 632, 634,636, 638 may be removed from the system 600 if not necessary for aparticular process to be performed by the system 600.

[0078] In one arrangement, each processing chamber 632 and 638 may be aphysical vapor deposition chamber, a chemical vapor deposition chamber,or a cyclical deposition chamber adapted to deposit a seed layer; eachprocessing chamber 634 and 636 may be a cyclical deposition chamber, achemical vapor deposition chamber, or a physical vapor depositionchamber adapted to deposit a barrier layer; each processing chamber 612and 614 may be a physical vapor deposition chamber, a chemical vapordeposition chamber, or a cyclical deposition chamber adapted to deposita dielectric layer; and each processing chamber 616 and 618 may be anetch chamber outfitted to etch apertures or openings for interconnectfeatures. This one particular arrangement of the system 600 is providedto illustrate the invention and should not be used to limit the scope ofthe invention.

[0079] It is believed that a refractory metal nitride layer having athickness greater than about 20 angstroms will terminate the growthpattern of the lower level metal interconnect. A refractory metalnitride layer having a thickness of about 20 angstroms or more willestablish a distinct growth pattern of its own, which would be initiallyadopted by the higher interconnect until the higher interconnect reachesa particular thickness and establishes its own pattern, thereby forminga different crystal structure. This phenomenon occurs because a growthpattern of a subsequently deposited layer typically resembles a growthpattern of an underlying layer during its initial stages of deposition,but the subsequent layer then takes on its own, inherent pattern oncethe subsequent layer reaches a particular thickness.

[0080] Tantalum nitride, for example, has a natural inclination to forman amorphous structure at about 20 angstroms or more. Below about 20angstroms, TaN resembles the growth pattern of its underlying layer.Therefore, a subsequent copper interconnect layer was surprisingly grownacross a barrier layer deposited according to the methods of the presentinvention exhibiting a similar growth pattern as the underlying copperinterconnect. In other words, a 20 angstroms or less TaN barrier layerenables good grain growth of copper such that copper grains can extendgrowth across the TaN barrier layer, or simply stated, copper exhibitsepitaxial growth on the tantalum nitride barrier layer.

[0081]FIG. 5 is a transmission electron microscope (TEM) image of afeature 300 having a titanium nitride barrier layer 310 depositedtherein according to the deposition techniques described above. Thefeature 300 had an aspect ratio of 5:1 and was formed on a 200 mm wafer.The barrier layer 310 consisted of tantalum nitride and was deposited at250° C. and 2 Torr. Each cycle lasted about 2 seconds and 30 cycles wereperformed. The tantalum nitride barrier layer 310 had a thickness ofabout 15 angstroms. As shown, the barrier layer 310 is conformal andshows good step coverage throughout the entire feature 300.

[0082]FIG. 6 is a TEM image showing a partial cross sectional view of amultilevel, interconnect structure 400. The multi-level, interconnectstructure 400 included a lower level copper interconnect 405, a tantalumnitride barrier layer 410, and an upper level copper interconnect 420.The copper grain growth of the lower level copper interconnect 405extended across the barrier layer 410 into the upper level copperinterconnect 420, showing epitaxial growth of the tantalum nitridebarrier layer 410. The barrier layer 410 consisted of tantalum nitrideand was deposited at 250° C. and 2 Torr. Each cycle lasted about 2seconds and 30 cycles were performed. The barrier layer 410 had athickness of about 10 angstroms, which was sufficient to inhibit coppermigration into the dielectric material.

[0083] The barrier layers 310, 410 shown and described with reference toFIGS. 3 and 4 were measured using a TEM instrument. It can beappreciated that a margin of error is present with this kind ofmeasurement technique as well as any other measurement technique fordetermining a thickness of a deposited layer. Therefore, the thicknessesprovided herein are approximate and quantified according to the bestavailable known techniques and are not intended to limit the scope ofthe present invention.

[0084] The following example is intended to provide a non-limitingillustration of one embodiment of the present invention.

EXAMPLE

[0085] A TaN layer was deposited over a lower level copper layer usingcyclical deposition to a thickness of about 20 Å. A copper alloy seedlayer was deposited over the TaN layer by physical vapor deposition to athickness of about 100 Å. The copper alloy seed layer contained aluminumin a concentration of about 2.0 atomic percent, and was deposited by PVDusing a copper-aluminum target consisting of aluminum in a concentrationof about 2.0 atomic percent. A bulk copper layer was then depositedusing ECP to fill the feature. The substrate was then thermally annealedat a temperature of about 380° C. for about 15 minutes in a nitrogen(N2) and hydrogen (H2) ambient.

[0086] The overall feature resistance was significantly reduced and theupper level copper layer surprisingly exhibited a grain growth similarto that of the lower level copper layer. The barrier performance of theTaN layer exhibited longer time to failure (TTF) compared with 50 Å PVDTa. Further, the TaN layer showed low contact resistance and a tightspread distribution. The TaN layer also exhibited excellent topographyincluding a smooth morphology and pinhole free surface.

[0087] Additionally, the TaN film deposited according to the PDMAT andammonia process described herein demonstrated exceptional filmuniformity. The film thickness was linearly proportional to the numberof deposition cycles, allowing accurate thickness control. Thicknessuniformity was found to be 1.8 percent for a 10 angstrom film and 2.1percent for a 100 angstrom film on a 200 mm substrate. The depositedfilms exhibited exceptionally conformal coverage, approaching 100percent in at least some results.

[0088] Finally, the copper alloy seed layer showed excellentadhesion/wetting to the TaN layer. The (PVD) copper seed layer exhibiteda preferred {111} orientation on the deposited barrier layer. Thecrystal orientation of {111} is preferred because this orientationprovides large grain sizes and exhibits good electromigration resistanceas a result of the larger grain sizes.

[0089] While the foregoing is directed to embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for forming a metal interconnect on a substrate, comprising:depositing a refractory metal containing barrier layer having athickness that exhibits a crystalline like structure and is sufficientto inhibit atomic migration on at least a portion of a metal layer byalternately introducing one or more pulses of a metal-containingcompound and one or more pulses of a nitrogen-containing compound;depositing a seed layer on at least a portion of the barrier layer; anddepositing a second metal layer on at least a portion of the seed layer.2. The method of claim 1, wherein the refractory metal containingbarrier comprises tantalum nitride.
 3. The method of claim 1, wherein agrain growth of the metal layer continues across the barrier layer intothe second metal layer.
 4. The method of claim 1, wherein each pulse isrepeated until the refractory metal containing barrier layer has athickness less than about 20 angstroms.
 6. The method of claim 1,wherein the refractory metal containing barrier layer has a thickness ofabout 10 angstroms.
 7. The method of claim 1, wherein the alternatepulsing is repeated between about 10 and about 70 times to form therefractory metal nitride layer.
 8. The method of claim 1, furthercomprising flowing a purge gas continuously during each pulse of themetal-containing compound and each pulse of the nitrogen-containingcompound.
 9. The method of claim 8, wherein the purge gas comprisesargon, nitrogen, helium, or combinations thereof.
 10. The method ofclaim 1, wherein each pulse of the metal-containing compound and thenitrogen-containing is separated by a time delay.
 11. The method ofclaim 10, wherein each time delay is long enough for a volume of themetal-containing compound or a volume of the nitrogen-containingcompound to adsorb onto the substrate surface.
 12. The method of claim11, wherein the time delay is long enough to remove non-adsorbedmolecules from the substrate surface.
 13. The method of claim 1, whereinthe nitrogen-containing compound is selected from a group consisting ofammonia; hydrazine; methylhydrazine; dimethylhydrazine;t-butylhydrazine; phenylhydrazine; azoisobutane; ethylazide; derivativesthereof; and combinations thereof.
 14. The method of claim 1, whereinthe metal-containing compound is selected from a group consisting of:tetrakis (dimethylamino) titanium (TDMAT); tetrakis (ethylmethylamino)titanium (TEMAT); tetrakis (diethylamino) titanium (TDEAT); titaniumtetrachloride (TiCl₄); titanium iodide (TiI₄); titanium bromide (TiBr₄);t-butylimino tris(diethylamino) tantalum (TBTDET); pentakis(ethylmethylamino); tantalum (PEMAT); pentakis (dimethylamino) tantalum(PDMAT); pentakis (diethylamino) tantalum (PDEAT); t-butyliminotris(diethyl methylamino) tantalum(TBTMET); t-butylimino tris(dimethylamino) tantalum (TBTDMT); bis(cyclopentadienyl) tantalum trihydride((Cp)₂TaH₃); bis(methylcyclopentadienyl) tantalum trihydride((CpMe)₂TaH₃); derivatives thereof; and combinations thereof.
 15. Themethod of claim 1, wherein the first and second metal layers eachcomprise tungsten, copper, or a combination thereof.
 16. The method ofclaim 1, wherein the seed layer comprises a first seed layer depositedover the barrier layer and a second seed layer deposited over the firstseed layer.
 17. The method of claim 16, wherein the first seed layercomprises a copper alloy seed layer of the copper and a metal selectedfrom the group consisting of aluminum, magnesium, titanium, zirconium,tin, and combinations thereof or wherein the first seed layer comprisesa metal selected from the group consisting of aluminum, magnesium,titanium, zirconium, tin, and combinations thereof.
 18. A method forforming a metal interconnect on a substrate, comprising: depositing afirst metal layer on a substrate surface; depositing a titanium siliconnitride layer having a thickness less than about 20 angstroms over atleast a portion of the first metal layer by alternately introducing oneor more pulses of a titanium-containing compound, one or more pulses ofa silicon-containing compound, and one or more pulses of anitrogen-containing compound; depositing a dual alloy seed layer; anddepositing a second metal layer on at least a portion of the dual alloyseed layer.
 19. A method for forming a metal interconnect on asubstrate, comprising: depositing a bilayer barrier having a thicknessless than about 20 angstroms on at least a portion of a metal layer, thebilayer barrier comprising: a first layer of tantalum nitride depositedby alternately introducing one or more pulses of a tantalum-containingcompound and one or more pulses of a nitrogen-containing compound; and asecond layer of alpha phase tantalum; depositing a dual alloy seedlayer; and depositing a second metal layer on at least a portion of thedual alloy seed layer.
 20. A method for forming a metal interconnect ona substrate, comprising: depositing a first metal layer on a substratesurface; depositing a tantalum nitride barrier layer having a thicknessless than about 20 angstroms on at least a portion of the first metallayer by alternately introducing one or more pulses of atantalum-containing compound and one or more pulses of anitrogen-containing compound; depositing a dual alloy seed layercomprising copper and a metal selected from the group consisting ofaluminum, magnesium, titanium, zirconium, tin, and combinations thereof;and depositing a second metal layer on at least a portion of the dualalloy seed layer.